Mounting arrangement for an adjusting cylinder in an axial compressor

ABSTRACT

The adjusting cylinder is moved axially by a pair of servomotors mounted on the casing exterior via piston rods which pass into the casing interior is seal-tight manner. Connecting rods having ball-headed ends connect the piston rods to the cylinders to compensate for radial movements of the adjusting cylinder relative to the casing.

United States Patent Benz 1451 Jan. 14, 1975 MOUNTING ARRANGEMENT FOR AN ADJUSTING CYLINDER IN AN AXIAL COMPRESSOR [75] Inventor: Hans Benz, Winterthur, Switzerland Assignee: Brown Boveri-Sulzer Turbomachinery Ltd., Zurich, Switzerland Filed: July 3, 1973 Appl. No.: 376,140

Foreign Application Priority Data July 13, 1972 Switzerland 010515/72 [56] References Cited UNITED STATES PATENTS 2,861,724 11/1958 Buch 415/157 3,094,270 6/1963 Kent et al 415/150 3,154,241 10/1964 Kent et al. 74/110 Primary Examiner-Everette A. Powell, Jr. Assistant Examiner-Louis J. Casaregola Attorney, Agent, or Firm-Kenyon & Kenyon Reilly Carr & Chapin [57] ABSTRACT The adjusting cylinder is moved axially by a pair of servomotors mounted on the casing exterior via piston rods which pass into the casing interior is seal-tight manner Connecting rods having ball-headed ends connect the piston rods to the cylinders to compensate for radial movements of the adjusting cylinder relative to the casing.

5 Claims, 2 Drawing Figures '1", L I P EA 1::-

E n"! l l :5 T 2 2 I l ll t I 11 l3 R 4 n 3 PATENTEBJAN v 41915 SHEEI 2 0F 2 MOUNTING ARRANGEMENT FOR AN ADJUSTING CYLINDER IN AN AXIAL COMPRESSOR Axial compressors have been known to have a casing defining an interior chamber sealed from an ambient zone as well as an adjusting cylinder within the chamber for adjusting the stator blades of the compressor. Generally, the adjusting cylinder is mounted for axial slideable movement by means of two linear servomotors which are connected in parallel to each other relative to the flow of working medium therein. However, the supervision and maintenance required for the hydraulic system for driving the adjusting cylinder calls for substantial expenditure and is frequently not possible without shutting down the plant. This is particularly true in the case of compressors in which the casing is under elevated pressure or in which the delivered gases are of the type which should not be discharged into the surrounding atmosphere. In addition, if the servomotors are disposed in the interior of the compressor or communicate therewith, care must be taken to avoid any risk of contomination of the gases passed through the compressors by leakage from the servomotors. Reference is made to US. Pat. No. 3,538,579 and Swiss Pat. No. 364,581 for axial compressors in which there is a device for adjusting the stator.

Accordingly, it is an object of the invention to separate the servomotors for adjusting the stator blades from the interior of the compressor casing and at the same time to provide reliable sealing at the positions which are the necessary for the piston rods to pass through into the casing interior.

It is another object of the invention to move an adjusting cylinder of a compressor from outside of a casing in which the cylinder is mounted.

It is another object of the invention to compensate for limited radial movements between a stator blade adjusting cylinder and a compressor casing.

Briefly, the invention provides a compressor construction in which an adjusting cylinder mounted within a gas-tight chamber of a casing is moved axially by means of e.g., servomotors, disposed outside the interior of the compressor and in which a sealing means is used to seal the piston rods of the servomotors relative to the casing to form a gas-tight seal. The sealing means is mounted on the external circumference of the piston rods for gas tight sealing at the positions at which the piston rods extend into the casing interior. Also, each piston rod is coupled to the adjusting cylinder by means of a connecting rod having ball head ends.

The ball-headed connecting rods ensure that, even in the event of relative displacements occurring between the cylinder and servomotors radially of the compressor due, for example, to installation inaccuracies and different thermal expansions resulting from different ambient temperatures and different materials between the compressor casing and the adjusting cylinder the pistons merely perform a motion which is centralized with respect to the axis of the servomotors and is performed in the direction of their axes. Thus, the seal elements are not loaded by deflections which are perpendicular to the direction of the axes and which might otherwise cause leakage. Furthermore, jamming of the servomotors is prevented by ensuring a purely axial motion of the piston rods.

In order to minimize the lateral forces transmitted by the ball heads to the piston rods, the distance between the point at which the ball head rod acts on the adjusting cylinder and the point at which the ball head rod acts on the piston rod should be as large as possible. Moreover, this point should be positioned as close as possible to the piston rod bearing. It is therefore advantageous if the piston rods have a length which corresponds to the length of stroke of the servomotor and their ends are provided with an extension sleeve that is open on one side and cooperates with the seals. It is of course also feasible to construct the free end of the piston rods in hollow form in order to achieve this effect. However, in terms of manufacturing technology. this solution would be unfavorable because it would render accessibility to the connection position more difficult.

The seal elements on the external circumference of the piston rods or the extension sleeves may also function as guides for a piston rod motion which is centered axially relative to the axis of the compressor.

These and other objects and advantages of the invention will become more apparent from the following detailed description and appended claims taken in conjunction with the accompanying drawings in which:

FIG. 1 diagrammatically illustrates a view of an axial compressor construction in accordance with the invention with the upper half of a casing which is divided in the horizontal axial plane removed; and

FIG. 2 illustrates a view taken along line [I II of FIG. I to an enlarged scale.

Referring to FIG. I, the compressor has an adjusting cylinder 1, comprising two part members of different diameters, which is supported in a casing 3 by means of rods 2 which are fixedly connected to the adjusting cylinder and are slidably mounted in support blocks 4 mounted in the casing 3. The cylinder 1 is axially slideable by means of two linear servomotors 5 which are mounted on the outside of the casing 3 separately from an internal chamber 6 defined by the casing 3 of the compressor. One of the servomotors 5 is controlled relative to a suitable operating variable, for example, the required delivery rate of the compressor. The other servomotor 5 cooperates without control but is in synchronism with the first servomotor 5.

The control of one servomotor 5 (the upper servomotor in FIG. 1) is indicated only by a return system comprising a disc cam 8 which is mounted on a piston rod 7 of the servomotor 5, and a bell crank 9 which slides on the disc cam 8 and, in turn, acts on a spool (not shown) which is disposed in a casing 10 and is conventionally used in hydraulic systems. Since the control for the servomotors 5 is conventional, no further description is believed to be necessary.

The motions of the piston rods 7 disposed in the servomotors 5 are transmitted to projections 13 which are secured to the adjusting cylinder 1, for example, by welding. As shown, the piston rods 7 extend into chambers 11 which communicate with the interior chamber 6 of the compressor and are sealed by seals 12. The projections 13 extend through slit apertures 21 in the casing 3 which communicate the interior chamber 6 with the chambers 11.

Referring to FIG. 2, connecting rods 14 are provided between the piston rods 7 and the associated projection 13 with each connecting rod 14 having ball head ends 15. The ball head ends 15 are each rotatbly received in a respective piston rod 7 and the adjusting cylinder l to form a universal joint at each end so as to compensate for radial movements between the cylinder 1 and casing 3. To this end, one ball head of each rod 14 engages in a corresponding recess 16 of the associated piston rod 7 and is retained by a nut 17 having external screwthreading and having a central aperture for passage of the rod 14. The other end 15 of each rod 14 bears in a bore 18 in a flanged end of a projection 13. In order to secure this end in place, on nut 17 having a central aperture is screwmounted in the bore 18 from one side and a second nut 19, which is not drilled but is provided with external screwthreading, is screwmounted from the other side. Both nuts 17, 19 have recesses 22 which are adapted to the ball head 15.

As already mentioned, the connection between the connecting rods 14 and the piston rods 7 is positioned as far as possible from the projection 13 and is disposed near the piston rod bearing 23 (FIG. 2) in the wall of the respective servomotor 5. The piston rod 7 is therefore kept as short as possible with a length corresponding approximately to the length of stroke of the piston (not shown) of the servomotor.

Each piston rod 7 is extended by having a tubular sleeve which is open at one end slidably mounted on the free end so that the connecting rod 14 is able, at any time, to carry out an unobstructed deflection in directions which are perpendicular to the rod axis. As shown, each connecting rod 14 is disposed concentrically within a sleeve 20 in spaced radial relation to allow for deflections of the rod 14.

The point of entry of the'sleeve 20 into the chamber 11 is sealed at the external circumference of the sleeve 20 since the shortened piston rod 7 does not extend at all or only slightly through the casing 3 into the chamber 11. To this end, a sealing means including a pair of seal elements 12 of conventional construction are used. These seal elements 12 are each supported in the compressor casing 3 and may take the form of glands with or without liquid barriers or may take the form of rubber seals. The seal elements 12 can be used, in conjunction with a bush 24 which is constructed of self lubricating material, to function as bearing and guide elements for the sleeve 20 attached to a piston rod 7.

What is claimed is:

1. In an axial compressor a casing defining a gas-tight internal chamber;

an adjusting cylinder for stator blades axially slidably mounted in said internal chamber within said casa pair of linear servomotors mounted on said casing exteriorly of said internal chamber, said servomotors being operatively connected in parallel relationship with each other, each said servomotor having a piston rod extending through said casing into said internal chamber;

a seal disposed on each piston rod for sealingly mounting each piston rod in said casing; and

a pair of connecting rods, each said connecting rod coupling one said piston rod to said adjusting cylinder, each said connecting rod having a ball head at each end rotatably received in a respective piston rod and in said adjusting cylinder.

2. In an axial compressor as set forth in claim 1, an extension sleeve mounted on each respective piston rod and projecting therefrom through said casing with a respective said seal thereon, each said piston rod being of a length corresponding to the length of stroke of a respective said servomotor.

3. In an axial compressor as set forth in claim 1, each said seal being mounted in said casing for guiding each respective piston rod for an axially centered motion.

4. In an axial compressor,

a casing defining a gas-tight internal chamber;

an adjusting cylinder for stator blades axially slidably mounted in said internal chamber within said casmeans mounted on said casing, exteriorly of said internal chamber, for moving said adjusting cylinder axially relative to said casing, said means including at least one servomotor having a piston rod and a connecting rod coupling said piston rod to said adjusting cylinder, said connecting rod being rotatably received in said piston rod and said adjusting cylinder so as to form a universal joint at either end thereof; and

sealing means sealing said piston rod relative to said casing to form a gas tight seal therebetween.

5. In an axial compressor as set forth in claim 4, said piston rod including an extension sleeve thereon projecting into said casing and having said sealing means thereon, said connecting rod being disposed concentrically within said sleeve in spaced radial relation. 

1. In an axial compressor a casing defining a gas-tight internal chamber; an adjusting cylinder for stator blades axially slidably mounted in said internal chamber within said casing; a pair of linear servomotors mounted on said casing exteriorly of said internal chamber, said servomotors being operatively connected in parallel relationship with each other, each said servomotor having a piston rod extending through said casing into said internal chamber; a seal disposed on each piston rod for sealingly mounting each piston rod in said casing; and a pair of connecting rods, each said connecting rod coupling one said piston rod to said adjusting cylinder, each said connecting rod having a ball head at each end rotatably received in a respective piston rod and in said adjusting cylinder.
 2. In an axial compressor as set forth in claim 1, an extension sleeve mounted on each respective piston rod and projecting therefrom through said casing with a respective said seal thereon, each said piston rod being of a length corresponding to the length of stroke of a respective said servomotor.
 3. In an axial compressor as set forth in claim 1, each said seal being mounted in said casing for guiding each respective piston rod for an axially centered motion.
 4. In an axial compressor, a casing defining a gas-tight internal chamber; an adjusting cylinder for stator blades axially slidably mounted in said internal chamber within said casing; means mounted on said casing, exteriorly of said internal chamber, for moving said adjusting cylinder axially relative to said casing, said means including at least one servomotor having a piston rod and a connecting rod coupling said piston rod to said adjusting cylinder, said connecting rod being rotatably received in said piston rod and said adjusting cylinder so as to form a universal joint at either end thereof; and sealing means sealing said piston rod relative to said casing to form a gas tight seal therebetween.
 5. In an axial compressor as set forth in claim 4, said piston rod including an extension sleeve thereon projecting into said casing and having said sealing means thereon, said connecting rod being disposed concentrically within said sleeve in spaced radial relation. 